WinCairo build fails to link.
https://bugs.webkit.org/show_bug.cgi?id=112892

Patch by peavo@outlook.com <peavo@outlook.com> on 2013-03-21
Reviewed by Kentaro Hara.

* WebKit.vcproj/WebKitExports.def.in: Added ENABLE(VIDEO_TRACK) guard.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146550 268f45cc-cd09-0410-ab3c-d52691b4dbfc